Contact Contact


Its principal aim is to measure and verify the precision of the watch movements and finished watches entrusted to it by manufacturers, in order to award them the official certified chronometer title.

The COSC’s human resources and the capabilities of its various premises enable the organisation to respond to all requests from the Swiss watch industry in terms of certification and chronometric controls.

The certified "chronometer” title, certifying the high level of precision and uniqueness of timekeeping instruments, is a guarantee of extreme quality, as well as the know-how applied throughout the production process. In the marketplace, it offers added value that enables beneficiaries to stand out from their competitors.


COSC : Contrôle Officiel Suisse des Chronomètres
Texte complémentaire


The COSC tests are carried out with absolute rigour:

  • The chronometric certification of wristwatches with a balance spring is based on 7 criteria set by the ISO 3159 standard, all of which must be fully met.
  • The chronometric certification of quartz watches, mechanical pocket watches or mechanical fixed timekeeping devices is based on internal requirements inspired by ISO 3159, but adapted to the specificities of the instruments.
  • Each piece examined daily for 14 to 20 days, depending on the type of instrument.
  • The certificate means that ALL the instruments entrusted to us are handled by agents of the COSC, a neutral and independent body.

The figures show a boom in COSC activity, with certifications seeing a significant increase.

  • 200,000 certificates in 1976
  • 1 million in 2000
  • between 2 and 2.3 million in recent years

Proof of the very high value to which the COSC "chronometer" certificate attests: only about 15% of Swiss watches exported have this status. (Source: Federation of the Swiss Watch Industry FH).




Annual report 2022




Plans to expand the premises have been initiated so that the infrastructure of our laboratories can meet the increase in the quantities deposited in the coming years. The operational security of the laboratories in the event of the closure of one of them for extraordinary reasons and the guarantee of the prompt handling of all the parts entrusted to us have been discussed again. Since 1 January 2022, the Biel laboratory has been responsible for its own production, while the Saint-Imier and Le Locle laboratories, in addition to their respective production, ensure the operational safety of the COSC. The expansion of the premises was completed at the end of 2022 in the Le Locle laboratory.

Read more
See all